Magnetoresistive effect element and magnetic memory

ABSTRACT

According to one embodiment, a magnetoresistive effect element includes: a first magnetic layer; a nonmagnetic layer provided on the first magnetic layer; a second magnetic layer provided on the nonmagnetic layer; a first insulating layer provided at least on a side surface of the second magnetic layer; a second insulating layer covering at least a part of the first insulating layer; a conductive layer provided between the first insulating layer and the second insulating layer; and a first electrode including a first portion on the second magnetic layer and a second portion on a side surface of the second insulating layer. A height of a lower surface of the second portion is equal to or less than a height of an upper surface of the conductive layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-220922, filed Nov. 11, 2016, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetoresistiveeffect element and a magnetic memory.

BACKGROUND

Magnetoresistive effect elements using magnetism such as hard diskdrives (HDD) and magnetic random access memories (MRAM) have beendeveloped.

A redeposit adhering to a side surface when the magnetoresistive effectelement is processed may be in contact with an electrode, which forms ashort-circuit path. A method for cutting the short-circuit path isrequired without damaging the element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a magnetoresistive effect element ofa first embodiment;

FIGS. 2A, 2B, 2C, 2D, and 2E illustrate a method for manufacturing themagnetoresistive effect element of the first embodiment;

FIGS. 3A, 3B, 3C, 3D, and 3E illustrate a method for manufacturing themagnetoresistive effect element of the first embodiment;

FIG. 4 is a cross-sectional view of a magnetoresistive effect element ofa second embodiment;

FIGS. 5A, 5B, 5C, 5D, 5E, and 5F illustrate a method for manufacturingthe magnetoresistive effect element of the second embodiment;

FIG. 6 is a cross-sectional view of a magnetoresistive effect element ofa third embodiment;

FIGS. 7A, 7B, 7C, 7D, 7E, 7F, and 7G illustrate a method formanufacturing the magnetoresistive effect element of the thirdembodiment;

FIG. 8 is a cross-sectional view of a magnetoresistive effect element ofa fourth embodiment;

FIGS. 9A, 9B, 9C, 9D, and 9E illustrate a method for manufacturing themagnetoresistive effect element of the fourth embodiment;

FIG. 10 shows an example of a magnetic storage device; and

FIG. 11 is a cross-sectional view showing a memory cell in the magneticstorage device.

DETAILED DESCRIPTION

In general, according to one embodiment, there is provided amagnetoresistive effect element comprising:

a first magnetic layer;

a nonmagnetic layer provided on the first magnetic layer;

a second magnetic layer provided on the nonmagnetic layer;

a first insulating layer provided at least on a side surface of thesecond magnetic layer;

a second insulating layer covering at least a part of the firstinsulating layer;

a conductive layer provided between the first insulating layer and thesecond insulating layer; and

a first electrode including a first portion on the second magnetic layerand a second portion on a side surface of the second insulating layer,wherein a height of a lower surface of the second portion is equal to orless than a height of an upper surface of the conductive layer.

Embodiments of the present invention will be described below withreference to the drawings. Those with the same reference numeralsindicate ones corresponding to each other. The drawings are schematic orconceptual, and the relationships between the thicknesses and widths ofportions, and the ratios of the sizes of portions or the like are notnecessarily the same as the actual values thereof. The dimensions andthe ratios may be illustrated differently between the drawings, even foridentical portions.

Herein, “on” and “above” represent the stacking direction of a laminate,and “side surface” and “side” represent a direction intersecting thestacking direction. Typical examples of the intersecting directioninclude, but not necessarily limited to, a perpendicular direction. Onthe other hand, a first direction represents the stacking direction ofthe laminate, and a second direction represents a direction intersectingthe first direction. Note that the stacking direction typicallycorresponds to a direction which connects two layers included in thelaminate to each other at the shortest distance.

First Embodiment

(Structure)

The structure of a magnetoresistive effect element of a first embodimentwill be described using FIG. 1.

As shown in FIG. 1, a magnetoresistive effect element A of the firstembodiment includes a lower electrode 11, a shift adjustment layer 12, aspacer layer 13, a first magnetic layer 14, a nonmagnetic layer 15, asecond magnetic layer 16, a first insulating layer 18, a secondinsulating layer 20, a first conductive layer 19, and an upper electrode17. The shift adjustment layer 12 is stacked on the lower electrode 11.The spacer layer 13 is stacked on the shift adjustment layer 12. Thefirst magnetic layer 14 is stacked on the spacer layer 13. Thenonmagnetic layer 15 is stacked on the first magnetic layer 14. Thesecond magnetic layer 16 is stacked on the nonmagnetic layer 15. Theupper electrode 17 includes a first portion 17 a and a second portion 17b. The first portion 17 a of the upper electrode 17 is stacked on thesecond magnetic layer 16, and the second portion 17 b is provided on aside surface of the first portion 17 a. That is, it can also be saidthat the first portion 17 a and the second portion 17 b face each otherin a second direction. The term “face” herein means that portions areopposed to each other. For example, the first portion 17 a and thesecond portion 17 b may be in contact with each other; the first portion17 a and the second portion 17 b may be separated; or other componentsmay exist between the first portion 17 a and the second portion 17 b.

In example of FIG. 1, the first magnetic layer 14 has a cross-sectionalarea S1. The second magnetic layer 16 has a cross-sectional area S2, andS2 is smaller than S1. The shift adjustment layer 12 and the spacerlayer 13 have substantially the same cross-sectional area S1, and thenonmagnetic layer 15 has substantially the same cross-sectional area S2as that of the second magnetic layer 16.

The first insulating layer 18 is provided so as to cover the sidesurface of the second magnetic layer 16 and the side surface of thenonmagnetic layer 15. The upper end part of the first insulating layer18 is positioned above the upper surface of the second magnetic layer16. The first conductive layer 19 is provided so as to be deposited onthe side surface of the first insulating layer 18, cover the sidesurface of the first insulating layer 18, and reach the vicinity of theupper electrode 17. The first conductive layer 19 is in contact with thefirst magnetic layer 14, and exists between the lower end part and upperend part of the first insulating layer 18 on the side surface of thefirst insulating layer 18. The first conductive layer 19 may not existup to the upper end part, or it may exist, for example, up to a positionlower than that of the upper end part. That is, the height of the upperend part of the first conductive layer 19 can be said to be equal to orgreater than the height of the lower surface of the second portion 17 bof the upper electrode 17. The side surfaces of the first conductivelayer 19, first magnetic layer 14, spacer layer 13, and shift adjustmentlayer 12 are covered with the second insulating layer 20 together withthe projecting portions of the first insulating layer 18 and firstconductive layer 19. That is, in the second direction, the firstinsulating layer 18 is provided to face the second magnetic layer 16 andthe first portion 17 a. The second insulating layer 20 is provided toface the first insulating layer 18, the first magnetic layer 14, thespacer layer 13, and the shift adjustment layer 12 in the seconddirection. The first conductive layer 19 exists between the firstinsulating layer 18 and the second insulating layer 20. At least a partof the second insulating layer is provided between the second portion 17b and the first conductive layer 19 in the second direction. The heightof the lower surface of the second portion 17 b is equal to or less thanthe height of the upper end part of the first conductive layer 19. Here,the height of the lower surface of the second portion 17 b refers to theheight of the lower surface at a position closest to the secondinsulating layer 20 (also including a case where the second portion 17 bis in contact with the second insulating layer 20).

It can also be said that the first insulating layer 18 surrounds thesecond magnetic layer 16 in a direction along a plane intersecting thefirst direction. It can also be said that the second insulating layer 20surrounds the first insulating layer 18 in the direction along the planeintersecting the first direction. That is, it can be said that the firstinsulating layer 18 surrounds the side of the second magnetic layer 16.It can also be said that the second insulating layer 20 surrounds theside of the first insulating layer 18. The “surround” may surround thecircumference, or may surround at least a part of the circumference.

A third insulating layer 21 exemplified in FIG. 1 is provided so as tocover the circumference of the magnetoresistive effect element A and bein contact with the lower electrode 11 and the upper electrode 17.

For example, each of the shift adjustment layer 12, the spacer layer 13,the first magnetic layer 14, the nonmagnetic layer 15, and the secondmagnetic layer 16 has a circular shape when viewed from the firstdirection. That is, each of the shift adjustment layer 12, the spacerlayer 13, the first magnetic layer 14, the nonmagnetic layer 15, and thesecond magnetic layer 16 has a cylindrical shape.

The lower electrode 11 and the third insulating layer 21 may not be incontact with each other regardless of example of FIG. 1. For example,the second insulating layer 20 may be provided between the lowerelectrode 11 and the third insulating layer 21, or an underlayer may beprovided between the lower electrode 11 and the third insulating layer21.

Regardless of the example of FIG. 1, the cross-sectional areas of theshift adjustment layer 12, spacer layer 13, first magnetic layer 14,nonmagnetic layer 15, and second magnetic layer 16 may be smaller inthis order.

In FIG. 1, the first insulating layer 18 covers the side surfaces of thenonmagnetic layer 15 and second magnetic layer 16, but it may cover atleast the side surface of the second magnetic layer 16.

In FIG. 1, the shift adjustment layer 12 and the spacer layer 13 areprovided between the lower electrode 11 and the first magnetic layer 14,but they may be omitted. In this case, the lower electrode 11 may be incontact with the first magnetic layer 14.

Although not shown in FIG. 1, an intermediate layer preventing theatomic diffusion of the magnetic layer and nonmagnetic layer may beprovided at the interface between the second magnetic layer 16 and thenonmagnetic layer 15 and at the interface between the first magneticlayer 14 and the nonmagnetic layer 15.

Regardless of the example of FIG. 1, a second conductive layerprotecting the magnetic layer 16 from damage due to hard mask removal orupper electrode formation, or the like may be provided between thesecond magnetic layer 16 and the upper electrode 17.

Although not shown in FIG. 1, an underlayer improving thecrystallinities of the shift adjustment layer 12 and magnetic layer 14may be provided between the lower electrode 11 and the shift adjustmentlayer 12.

(Operating Principle)

Magnetic tunnel junction is formed by the first magnetic layer 14, thesecond magnetic layer 16, and the nonmagnetic layer 15 sandwichedtherebetween. Hereinafter, the magnetoresistive effect element is alsoreferred to as an MTJ element.

The first magnetic layer 14 and the second magnetic layer 16 contain amaterial having magnetic property, and the first magnetic layer 14 andthe second magnetic layer 16 are also collectively referred to as amagnetic layer. The direction of magnetization of the second magneticlayer 16 is variable. The direction of magnetization of the firstmagnetic layer 14 is in a fixed state, and has a predetermineddirection. The second magnetic layer 16 whose the direction ofmagnetization is variable is also referred to as a storage layer, avariable layer, and a magnetization free layer, and the first magneticlayer 14 whose the direction of magnetization is in a fixed state isalso referred to as a reference layer or a fixed layer. Arrows in thefirst magnetic layer 14 and the second magnetic layer 16 in FIG. 1represent the directions of magnetization of the first magnetic layer 14and second magnetic layer 16.

Perpendicular magnetization will be described using FIG. 1. The firstmagnetic layer 14 and the second magnetic layer 16 have magneticanisotropy in a direction perpendicular or substantially perpendicularto a layer surface. The directions of easy magnetization of the secondmagnetic layer 16 and first magnetic layer 14 are perpendicular orsubstantially perpendicular to the layer surface of the magnetic layer.In the direction of easy magnetization (magnetic anisotropy)perpendicular or substantially perpendicular to the layer surface,magnetization facing the direction perpendicular or substantiallyperpendicular to the layer surface is referred to as perpendicularmagnetization. Therefore, the MTJ element of the present embodiment is aperpendicular magnetization type MTJ element.

The direction of easy magnetization is a direction in which, when aferromagnetic substance of a certain macro size is assumed, internalenergy of the magnetic substance becomes the lowest if spontaneousmagnetization is oriented in the direction in a state in which there isno external magnetic field.

Next, a data retention mechanism of the MTJ element of the presentembodiment will be described. The first magnetic layer 14 and the secondmagnetic layer 16 are positioned between the two electrodes 11 and 17.When a magnetization switching current is supplied to the secondmagnetic layer 16 via the electrodes 11 and 17, the angular momentum ofspin-polarized electrons generated by the current is transferred to themagnetization (spin) of the second magnetic layer 16. The direction ofmagnetization of the second magnetic layer 16 is thereby reversed. Thatis, the direction of magnetization of the second magnetic layer 16 isvariable according to the direction in which the current flows. Themagnetization switching current is a current for reversing the directionof magnetization.

On the other hand, the magnetization switching current is supplied toalso the first magnetic layer 14 via the electrodes 11 and 17 in thesame manner. In this case, the direction of magnetization of the firstmagnetic layer 14 is in a fixed state, and is maintained in apredetermined direction. The direction of magnetization of the firstmagnetic layer 14 being “maintained in a predetermined direction” or “ina fixed state” means that, when the magnetization switching current ofthe second magnetic layer 16 supplied between the two electrodes fromthe outside flows through the first magnetic layer 14, the direction ofmagnetization of the first magnetic layer 14 is kept in a predetermineddirection when the direction of magnetization before flowing is comparedwith that after flowing.

Therefore, in the MTJ element A, a magnetic layer having a largemagnetization switching current supplied via the two electrodes 11 and17 from the outside is used as the first magnetic layer 14, and amagnetic layer having a smaller magnetization switching current suppliedvia the two electrodes 11 and 17 than that of the first magnetic layer14 is used as the second magnetic layer 16, so that the MTJ element A isformed, which includes the second magnetic layer 16 whose the directionof magnetization is variable and the first magnetic layer 14 whose thedirection of magnetization is maintained.

When magnetization reversing is caused by spin-polarized electrons, themagnitude of the magnetization switching current thereof is proportionalto the damping constant, magnetic coercive force, anisotropic magneticfield, and volume of the magnetic layer. Thus, a difference between themagnetization switching current of the second magnetic layer 16 and themagnetization switching current of the first magnetic layer 14 can beprovided by the above values being appropriately adjusted.

When the magnetization switching current of the second magnetic layer 16supplied through the two electrodes 11 and 17 is supplied to the MTJelement A, the direction of magnetization of the second magnetic layer16 changes in accordance with the direction in which the current flows,and the relative magnetization arrangement of the first magnetic layer14 and second magnetic layer 16 changes. Accordingly, the MTJ element Ais in either a high resistance state (state in which the magnetizationarray is antiparallel) or a low resistance state (state in which themagnetization array is parallel), which can hold data.

(Materials of Layers)

The lower electrode 11 is preferably formed of a material having lowelectric resistance and excellent diffusion resistance. The lowerelectrode 11 may function as a buffer layer in order to grow a flatmagnetic layer having perpendicular magnetization. The lower electrode11 has a laminated structure including a metal layer of tantalum (Ta),copper (Cu), ruthenium (Ru), or iridium (Ir) or the like.

A material used for the upper electrode 17 preferably has low electricalresistance and diffusion resistance. As the material of the upperelectrode 17, for example, Ta is used.

The spacer layer 13 is formed of a metal such as ruthenium (Ru) or Ta.

A conductive ferromagnetic material having an L1 ₀ structure or an L1 ₁structure such as FePd, FePt, CoPd, or CoPt, a conductive material suchas CoFeB, and a conductive ferrimagnetic material such as TbCoFe areused as the material of the first magnetic layer 14. The first magneticlayer 14 may be a conductive artificially layered structure formed of amagnetic material (for example, NiFe, Fe, or Co or the like) and anonmagnetic material (Cu, Pd, or Pt or the like).

A shift adjustment layer (also referred to as a shift correcting layeror a bias magnetic field layer) 12 is provided so as to be adjacent tothe first magnetic layer 14 in order to bring the magnetic field fromthe first magnetic layer 14 to the second magnetic layer 16 closer tozero. The magnetization of the shift adjustment layer 12 is in a fixedstate, and the direction of magnetization of the shift adjustment layeris set opposite to the direction of magnetization of the first magneticlayer 14. For example, the shift adjustment layer 12 is formed of thesame material as the first magnetic layer 14.

An insulating material such as magnesium oxide (MgO), magnesium nitride(MgN), aluminum oxide (Al₂O₃), aluminum nitride (AlN), or a stacked filmthereof is used as the material of the nonmagnetic layer 15. Forexample, the nonmagnetic layer 15 is formed of an insulating filmcontaining MgO as a main component. A nonmagnetic metal or a nonmagneticsemiconductor may be used for the nonmagnetic layer 15.

The second magnetic layer 16 is formed of a magnetic material containingan element in the fourth period (from the atomic number 19 to the atomicnumber 36). For example, one or more elements selected from the groupconsisting of manganese (Mn), iron (Fe), and cobalt (Co) are containedas a main component. Nickel (Ni) may be used as a magnetic elementinstead of Mn, Fe and Co. The second magnetic layer 16 may contain boron(B) in addition to at least one of Mn, Fe and Co. The second magneticlayer 16 is formed of, for example, CoFeB.

As the first insulating layer 18, an insulator formed of HfN or the likeis used.

The first conductive layer 19 is a film containing, for example, one ormore of Fe, Pd, Pt, and Co or the like.

The second insulating layer 20 is an insulator having higher physicaletching resistance than that of the third insulating layer 21, and forexample, AlO or the like is used.

For the third insulating layer 21, an insulating film formed of SiN orSiO or the like is used.

The material of the intermediate layer (not shown) is CoFeB or the like.By providing the intermediate layer, characteristics such as preventionof the atomic diffusion of the magnetic layer and nonmagnetic layer 15can be improved.

The material of the second conductive layer (not shown) is, for example,Ta or Pt or the like. By providing the second conductive layer, themagnetic layer 16 can be protected from damage due to hard mask removalor upper electrode formation.

The material of the underlayer (not shown) is a conductor containing,for example, Ta, Ru, and Hf or the like. By providing the underlayer,the crystallinities of the shift adjustment layer 12 and magnetic layer14 can be improved.

(Manufacturing Method)

The manufacturing method of an MTJ element A of the first embodimentwill be described using FIGS. 2A to 2E and FIGS. 3A to 3E.

FIGS. 2A to 2E and FIGS. 3A to 3E are cross-sectional step chartsillustrating steps of the manufacturing method of an MTJ elementaccording to the present embodiment.

First, a shift adjustment layer 12, a spacer layer 13, a first magneticlayer 14, a nonmagnetic layer 15, a second magnetic layer 16, and a hardmask 23 are deposited in this order from the side of a lower electrode11 on the lower electrode 11 using the sputtering method or the atomiclayer deposition (ALD) method or the like. As a result, a laminatedstructure (processed layer) 1Z for forming a top free type MTJ elementis formed (FIG. 2A).

The sputtering method or the ALD method or the like is also used fordepositing an intermediate layer (not shown), a second conductive layerand an underlayer.

The hard mask 23 provided on the upper surface of the second magneticlayer 16 is processed into a pattern 23A having a predetermined shape(for example, a cylindrical shape having a cross-sectional area S2(S2<S1) and a height d) by lithography and etching, and the pattern 23Aused as a mask for processing the laminated structure 1Z including thefirst magnetic layer 14, the second magnetic layer 16, and the shiftadjustment layer 12 is formed on the upper surface of the laminatedstructure 1Z (FIG. 2B).

The ion milling of the laminated structure 1Z is performed using thepattern 23A as a mask.

The ion milling for processing the laminated structure 1Z is ion millingusing an inert gas such as argon (Ar), krypton (Kr), or xenon (Xe). Inthe present embodiment, the laminated structure 1Z is processed by ionmilling using Ar. The laminated structure 1Z may be processed by etchingusing gas cluster ions.

The incident angle θ of an ion (ion beam) with respect to the laminatedstructure 1Z in the ion milling is set to, for example, about 50° withthe direction perpendicular to the layer surface of the processed layerincluded in the laminated structure 1Z as a reference angle (0°).

By performing the ion milling using the upper surface of the firstmagnetic layer 14 as a stopper, as shown in FIG. 2C, the second magneticlayer 16 and nonmagnetic layer 15 having a shape corresponding to thepattern 23A of the hard mask 23 are formed on the first magnetic layer14.

A first insulating layer 18 having a predetermined layer thickness T1(for example, 3 nm) is formed so as to cover the pattern 23A, the secondmagnetic layer 16, and the nonmagnetic layer 15 (FIG. 2D).

The first insulating layer 18 may be formed using a vacuum filmformation technique such as ion beam sputtering, ion plating, vacuumdeposition, ALD method, or CVD method, and then insulated by naturaloxidation or oxygen-nitrogen plasma or the like.

The first insulating layer 18 on the side surfaces of the secondmagnetic layer 16 and nonmagnetic layer 15 is formed of one materialselected from HfN and WN or the like, for example.

After the first insulating layer 18 is formed, the first insulatinglayer 18 except the side surface of the nonmagnetic layer 15, the sidesurface of the second magnetic layer 16, and the side surface of thepattern 23A is removed by ion milling. Furthermore, when ion milling isperformed again along the side surface of the first insulating layer 18,the first magnetic layer 14, spacer layer 13, and shift adjustment layer12 having a predetermined shape (for example, the cross-sectional areasS1 of the shift adjustment layer 12, spacer layer 13, and first magneticlayer 14) are formed. At that time, a first conductive layer 19 isformed so as to cover the side surface of the first insulating layer 18(FIG. 2E).

The first conductive layer 19 is a residue generated by ion milling.When the ion milling of FIG. 2E is performed, a residue derived from thefirst magnetic layer 14 is deposited so as to cover the side surface ofthe first insulating layer 18, to form the first conductive layer 19.

As shown in FIG. 3A, after the MTJ element having a predetermined shape(for example, the cross-sectional area S1 of the first magnetic layer14) is formed by processing the laminated structure, the hard mask 23(pattern 23A) is removed by, for example, oxygen plasma etching or thelike.

A second insulating layer 20 having a predetermined layer thickness T1(for example, 3 nm) is formed so as to cover the side surface of theshift adjustment layer 12, the side surface of the spacer layer 13, thefirst magnetic layer 14, the upper surface of the second magnetic layer16, the first insulating layer 18, and the first conductive layer 19(FIG. 3B). At this time, by forming the film at an angle, the secondinsulating layer 20 on the second magnetic layer 16 can be thinner thanthe second insulating layer 20 on the upper and side surfaces of thefirst conductive layer 19.

The second insulating layer 20 may be formed using a vacuum filmformation technique such as ion beam sputtering, ion plating, vacuumdeposition, ALD method, or CVD method, and then insulated by naturaloxidation or oxygen-nitrogen plasma or the like.

After the second insulating layer 20 is formed, a third insulating layer21 is deposited by, for example, the CVD method so as to cover the MTJelement as the laminated structure including the first insulating layer18 (FIG. 3C).

As shown in FIG. 3D, the third insulating layer 21 is removed until theupper surface of the third insulating layer 21 is positioned at the samelevel as or at a level lower than that of the upper surface of thesecond magnetic layer 16, for example, by ion milling after the thirdinsulating layer 21 is formed (FIG. 3D). At this time, since the secondinsulating layer 20 has higher ion milling resistance than that of thethird insulating layer 21, the second insulating layer 20 remains on theupper and side surfaces of the first conductive layer 19. However, thethin portion of the second insulating layer 20 formed on the uppersurface of the second magnetic layer 16 is scraped, to expose the secondmagnetic layer 16.

After the second magnetic layer 16 is exposed, an upper electrode 17 isformed on the second magnetic layer 16, the second insulating layer 20,and the third insulating layer 21 by, for example, the sputtering method(FIG. 3E).

Through the above manufacturing step, the MTJ element A of the firstembodiment is formed.

Here, in the conventional manufacturing method, a short circuit causedby a side deposit when the first magnetic layer 14 is formed is feared.In particular, when the first magnetic layer 14 is formed of a materialdifficult to be insulated, such as Pt or Pd, the material is consideredto have a large influence. The step of removing the redeposit by ionmilling or the like after the first magnetic layer 14 is formed has ahigh probability of damaging the side surface of the MTJ element by ionmilling, and the influence of side damage cannot be ignored in a minuteMTJ element of 20 nm or less. A method such as controlling so as toprevent the redeposit from adhering according to the condition of ionmilling when the first magnetic layer 14 is formed makes it difficult tocompletely suppress the short circuit.

In the MTJ element A of the first embodiment, the first conductive layer19 is formed, and the second insulating layer 20 is then formed, whichmakes it possible to surely prevent the contact of the first conductivelayer 19 with the upper electrode 17 without damaging the MTJ element.

The second insulating layer 20 may cover at least a part of the firstconductive layer so as to prevent the contact of the first conductivelayer 19 with the upper electrode 17.

Second Embodiment

Hereinafter, an MTJ element B of a second embodiment and a method formanufacturing the same will be described with reference to FIG. 4 andFIGS. 5A to 5F.

In the present embodiment, the descriptions of constituent elementscommon to those in the first embodiment are made as necessary.

The structure of the MTJ element B of the second embodiment will bedescribed using FIG. 4.

In the MTJ element A of the first embodiment shown in FIG. 1, the secondinsulating layer 20 is provided along the first conductive layer 19.However, as shown in FIG. 4, the MTJ element B of the second embodimenthas a structure in which a second insulating layer 20 is provided alonga third insulating layer 21, and covers a protruding first insulatinglayer 18 and first conductive layer 19.

The method for manufacturing the MTJ element B of the second embodimentwill be described using FIGS. 5A to 5F. Here, the method formanufacturing the MTJ element B of the present embodiment will bedescribed by appropriately using FIGS. 2A to 2E.

FIGS. 5A to 5F are cross-sectional step charts illustrating steps of themethod for manufacturing the MTJ element B of the present embodiment.

First, as in the first embodiment, the steps of FIGS. 2A to 2E areperformed.

Next, the steps will be described using FIGS. 5A to 5F.

After an MTJ element having a predetermined shape is formed byprocessing a laminated structure, a third insulating layer 21 isdeposited, for example, by the CVD method so as to cover an MTJ elementas the laminated structure including a first insulating layer 18 (FIG.5A).

After the third insulating layer 21 is formed, the third insulatinglayer 21 is removed by, for example, ion milling until an upper surfaceof the third insulating layer 21 is lower than the interface between ahard mask 23 and a second magnetic layer 16 (FIG. 5B).

Ion milling may be performed so that the upper surface of the thirdinsulating layer 21 is above an upper surface of the magnetic layer 16when the third insulating layer 21 is removed regardless of FIG. 5B.

After the third insulating layer 21 is removed, the hard mask 23(pattern 23A) is removed by, for example, oxygen plasma etching or thelike (FIG. 5C).

A second insulating layer 20 having a predetermined layer thickness T1(for example, 3 nm) is formed by, for example, the sputtering method soas to cover a first conductive layer 19, the upper surface of the thirdinsulating layer 21, and the upper surface of the MTJ element. At thistime, by forming the film at an angle, the second insulating layer 20 onthe second magnetic layer 16 can be thinner than the second insulatinglayer 20 on the upper and side surfaces of the first conductive layer 19(FIG. 5D) (for example, 1 nm or less).

After the second insulating layer 20 is formed, the second insulatinglayer 20 of the second magnetic layer 16 is removed by, for example,sputter etching or the like. At this time, the second insulating layer20 deposited on the other portion remains without being completelyremoved because the second insulating layer 20 is thick (FIG. 5E).

After the second magnetic layer 16 is exposed, an upper electrode 17 isformed on the upper surface of the second magnetic layer 16, the secondinsulating layer, and the third insulating layer 21 by, for example, thesputtering method (FIG. 5F).

Through the above manufacturing step, the MTJ element B of the secondembodiment is formed.

The contact of the first conductive layer 19 with the upper electrode 17can be reliably prevented without damaging the MTJ element as in thefirst embodiment. Since the second insulating layer is formed along theupper surface of the third insulating layer 21 in the MTJ element B ofthe present embodiment, the manufacturing step is simpler than that ofthe MTJ element A. Specifically, in the MTJ element A of the firstembodiment, the step of exposing the upper part of the MTJ element A isperformed by removing the third insulating layer 21 by ion milling in astate where the second insulating layer 20 is formed. The secondinsulating layer 20 is considerably harder than the third insulatinglayer 21, which makes it difficult to remove the third insulating layer21 formed in a recessed portion in the upper part of the MTJ element. Onthe other hand, since the second insulating layer 20 is formed after thestep of exposing the upper part of the MTJ element in the secondembodiment, the hardness of the second insulating layer 20 is notlimited. Since the pattern 23A is removed after the step of exposing theupper part of the MTJ element, the third insulating layer 21 is notformed in the recess in the upper part of the MTJ element. So, there isno concern as described above, and the manufacturing step is simplerthan that of the MTJ element A.

Third Embodiment

Hereinafter, with reference to FIG. 6 and FIGS. 7A to 7G, an MTJ elementC of a third embodiment and a method for manufacturing the same will bedescribed.

In the present embodiment, the descriptions of constituent elementscommon to those in the second embodiment are made as necessary.

(Structure)

The structure of the MTJ element C of the third embodiment will bedescribed using FIG. 6.

The difference between the MTJ element B of the second embodiment shownin FIG. 4 and the MTJ element C of the third embodiment is that the MTJelement C has a fourth insulating layer 22 covering the side surfaces ofa shift adjustment layer 12, spacer layer 13, first magnetic layer 14,and first conductive layer 19, as shown in FIG. 6. That is, the fourthinsulating layer 22 is in contact with also a third insulating layer 21.It can be said that the fourth insulating layer 22 faces the shiftadjustment layer 12, the spacer layer 13, the first magnetic layer 14,and the first conductive layer 19 in a second direction.

The material of the fourth insulating layer 22 is, for example, SiN.

(Manufacturing Method)

A method for manufacturing the MTJ element C of the third embodimentwill be described using FIGS. 7A to 7G. Herein, the method formanufacturing the MTJ element C of the present embodiment will bedescribed appropriately using FIGS. 2A to 2E.

FIGS. 7A to 7G are cross-sectional step charts illustrating steps of themanufacturing method of an MTJ element according to the presentembodiment.

First, as in the second embodiment, the steps of FIGS. 2A to 2E areperformed.

The steps will be described using FIGS. 7A to 7G.

After an MTJ element having a predetermined shape is formed byprocessing a laminated structure, a fourth insulating layer 22 isdeposited on a substrate, for example, by the CVD method so as to coverthe MTJ element (FIG. 7A).

Next, a third insulating layer 21 is deposited on the substrate by, forexample, the sputtering method so as to cover the MTJ element (FIG. 7B).

After the third insulating layer 21 is formed, the third insulatinglayer 21 is removed by, for example, ion milling until the upper surfaceof the third insulating layer 21 is at the same level as or at a levellower than that of the upper surface of the second magnetic layer 16(FIG. 7C). Ion milling may be performed so that the upper surface of thethird insulating layer 21 is located above the upper surface of themagnetic layer 16 when the third insulating layer 21 is removedregardless of FIG. 7B.

After the third insulating layer 21 is removed, a hard mask 23 (pattern23A) is removed by, for example, oxygen plasma etching or the like (FIG.7D).

A second insulating layer 20 having a predetermined layer thickness T1(for example, 3 nm) is formed by, for example, the sputtering method soas to cover a first conductive layer 19, the upper surface of the thirdinsulating layer 21, and the upper surface of the MTJ element. At thistime, by forming the film at an angle, the second insulating layer 20 onthe second magnetic layer 16 can be thinner than the second insulatinglayer 20 on the upper and side surfaces of the first conductive layer 19(FIG. 7E) (for example, 1 nm or less).

After the second insulating layer 20 is formed, the insulating layer ofthe second magnetic layer 16 is removed by, for example, sputter etchingor the like. At this time, the second insulating layer 20 deposited onthe other portion remains without being completely removed because thesecond insulating layer 20 is thick (FIG. 7F).

After the second magnetic layer 16 is exposed, an upper electrode 17 isformed on the upper surface of the second magnetic layer 16, the secondinsulating layer 20, and the third insulating layer 21 by, for example,the sputtering method (FIG. 7G).

Through the above manufacturing step, the MTJ element C of the thirdembodiment is formed.

As in the first embodiment, the MTJ element C of the present embodimentcan prevent the contact of the first conductive layer 19 with the upperelectrode 17 without damaging the MTJ element. The third embodiment canbe more simply manufactured than the first embodiment for the samereason as that in the second embodiment. Furthermore, in the thirdembodiment, by providing the MTJ element with the fourth insulatinglayer 22, external factors such as natural oxidation in themanufacturing step can be prevented.

Fourth Embodiment

Hereinafter, an MTJ element D of a fourth embodiment and a method formanufacturing the same will be described with reference to FIGS. 8 and9A to 9E.

In the present embodiment, the descriptions of constituent elementscommon to those in the first embodiment are made as necessary.

The structure of the MTJ element D of the fourth embodiment will bedescribed using FIG. 8.

In the MTJ element A of the first embodiment shown in FIG. 1, a firstinsulating layer 18 is formed so as to cover the side surfaces of anonmagnetic layer 15 and second magnetic layer 16. However, in the MTJelement D of the fourth embodiment shown in FIGS. 9A to 9E, the firstinsulating layer 18 covers the side surface of the second magnetic layer16. That is, in a second direction, the first insulating layer 18 doesnot face the nonmagnetic layer 15 but faces a second portion 17 b andthe second magnetic layer 16.

(Manufacturing Method)

A method for manufacturing the MTJ element D of the fourth embodimentwill be described using FIGS. 9A to 9E. Herein, the method formanufacturing the MTJ element D of the present embodiment will bedescribed by appropriately using FIGS. 3A to 3E.

FIGS. 9A to 9E are cross-sectional step charts illustrating steps of themanufacturing method of the MTJ element D according to the presentembodiment.

As in the first embodiment, a shift adjustment layer 12, a spacer layer13, a first magnetic layer 14, a nonmagnetic layer 15, a second magneticlayer 16, and a hard layer 23 are first deposited in this order from theside of a lower electrode 11 on the lower electrode 11 by the sputteringmethod or the ALD method or the like. As a result, a laminated structure(processed layer) 1Z for forming a top free type MTJ element is formed(FIG. 9A).

The sputtering method or the ALD method or the like is also used fordepositing an intermediate layer (not shown), a second conductive layerand an underlayer.

The hard mask 23 provided on the upper surface of the second magneticlayer 16 is processed into a pattern 23A having a predetermined shape(for example, a cylindrical shape having a cross-sectional area S2(S2<S1) and a height d) by lithography and etching. The pattern 23A usedas a mask for processing the laminated structure 1Z including the firstmagnetic layer 14, the second magnetic layer 16, and the shiftadjustment layer 12 is formed on the upper part of the laminatedstructure 1Z (FIG. 9B).

The ion milling of the laminated structure 1Z is performed using thepattern 23A as a mask.

By performing ion milling using the upper surface of the nonmagneticlayer 15 as a stopper, as shown in FIG. 9C, the second magnetic layer 16having a shape corresponding to the pattern 23A of the hard mask 23 isformed on the nonmagnetic layer 15.

A first insulating layer 18 having a predetermined layer thickness T1(for example, 3 nm) is formed so as to cover the pattern 23A and thesecond magnetic layer 16 (FIG. 9D).

After the first insulating layer 18 is formed, the first insulatinglayer 18 except the side surfaces of the second magnetic layer 16 andpattern 23A is removed by ion milling. Furthermore, when the ion millingis performed again along the side surface of the first insulating layer18, the shift adjustment layer 12, spacer layer 13, first magnetic layer14, and nonmagnetic layer 15 having a predetermined shape (for example,the cross-sectional areas S1 of the shift adjustment layer 12, spacerlayer 13, and first magnetic layer 14, and the cross-sectional area S1/2(S1>S1/2>S2) of the nonmagnetic layer 15) are formed. At that time, afirst conductive layer 19 is formed so as to cover the side surfaces ofthe first insulating layer 18 and nonmagnetic layer 15 (FIG. 9E).

Then, as in the first embodiment, the steps of FIGS. 3A to 3E areperformed. However, the steps of FIGS. 3A to 3E are performed while theside surface of the nonmagnetic layer 15 is covered with the firstconductive layer 19. That is, the steps of FIGS. 3A to 3E are performedwithout the first insulating layer 18 covering the side surface of thenonmagnetic layer 15.

Through the above manufacturing step, the MTJ element D of the fourthembodiment is formed.

In the case where a material having high ion milling resistance is usedfor the nonmagnetic layer 15, stopping ion milling on the upper surfaceof the nonmagnetic layer 15 is easier than stopping on the upper surfaceof the first magnetic layer 14 of the first embodiment. That is, the MTJelement D can be more easily produced than the MTJ element A in themanufacturing step.

[Application Example of Embodiment]

Application example of the above-described embodiment will be describedusing FIGS. 10 and 11. The MTJ element A of the present embodiment isused as a memory element of a magnetic memory, for example, an MRAM. Inthe present application example, a spin-torque transfer MRAM (STT-MRAM)is exemplified.

(Basic Configuration of Application Example)

As shown in FIG. 10, the STT-MRAM of the present application exampleincludes an MTJ element A, column control circuits 3A and 3B, a rowcontrol circuit 4, write circuits 5A and 5B, and a read circuit 6A.

A memory cell array MCA includes a plurality of memory cells MC. Theplurality of memory cells MC are arranged in an array form in the memorycell array MCA. In the plurality of memory cells MC, a plurality of bitlines BL and bBL extending in the memory cell array MCA extend in acolumn direction, and are connected to a word line WL. The bit lines BLand bBL extend in the column direction, and the word lines WL extend ina row direction. The two bit lines BL and bBL form a bit line pair.

The memory cell MC includes one MTJ element A and one select transistor2. The select transistor 2 is, for example, a field effect transistor.

One end of the MTJ element A is connected to the bit line BL, and theother end of the MTJ element A is connected to one end (source/drain) ofa current path of the select transistor 2. The other end (drain/source)of the current path of the select transistor 2 is connected to the bitline bBL. A control terminal (gate) of the select transistor 2 isconnected to the word line WL.

As described above, the plurality of memory cells MC arranged in thecolumn direction are connected to the common bit line pair (BL, bBL).

The column control circuit 3A is connected to one ends of the bit linesBL and bBL, and the column control circuit 3B is connected to the otherends of the bit lines BL and bBL. The column control circuits 3A and 3Bcontrol the activation and deactivation of the bit lines BL and bBLbased on an address signal from the outside. One end of the word line WLis connected to the row control circuit 4. The row control circuit 4controls the activation and inactivation of the word line WL based on anaddress signal from the outside.

The write circuits 5A and 5B are connected to one ends and the otherends of the bit lines BL and bBL via the column control circuits 3A and3B, respectively. Each of the write circuits 5A and 5B includes a sourcecircuit such as a current source for generating a write current I_(WR)or a voltage source and a sink circuit for sinking the write currentI_(WR).

The read circuit 6A is connected to the bit lines BL and bBL via thecolumn control circuit 3A. The read circuit 6A includes a voltage sourceor a current source for generating a read current, a sense amplifier fordetecting and amplifying a read signal, and a latch circuit fortemporarily holding data, or the like.

When data is written to the MTJ element A, a write current is suppliedto the memory cell MC.

When data is written to the MTJ element A, the write circuits 5 A and 5Bbidirectionally flow the write current I_(WR) to the MTJ element A inthe memory cell MC according to data to be written to the memory cellMC. That is, the write current I_(WR) from the bit line BL to the bitline bBL or the write current I_(WR) from the bit line bBL to the bitline BL is output from the write circuits 5A and 5B according to thedata to be written to the MTJ element A.

The read circuit 6A supplies a read current to the memory cell MC whendata is read from the MTJ element A.

The current value of the write current I_(WR) is set to be larger than amagnetization reversing threshold value. The current value of the readcurrent is set smaller than the magnetization reversing threshold valueso that the magnetization of the storage layer of the MTJ element A isnot reversed by the read current.

The current value or the potential is different depending on themagnitude of the resistance value of the MTJ element A to which the readcurrent is supplied. Data stored in the MTJ element A is determined onthe basis of a variation amount (read signal, read output) according tothe magnitude of the resistance value.

In addition to the above components, the MTJ element A in the memorycell MC, for example, the MTJ element A according to the above-describedembodiment may be the MTJ element B, the MTJ element C, or the MTJelement D. For example, a buffer circuit, a state machine (controlcircuit), or an ECC (Error Checking and Correcting) circuit or the likemay be provided in the same chip as the memory cell array MCA.Furthermore, in the STT-MRAM, the two read circuits 6A may berespectively provided on one end and the other end of the memory cellarray MCA in the column direction, regardless of the example of FIGS. 10and 11.

(Structure of Memory Cell)

In FIG. 11, the memory cell MC is formed in an active region of asemiconductor substrate 30. The active region is partitioned by aninsulating film 31 embedded in an element isolation region of thesemiconductor substrate 30. The semiconductor substrate 30 is coveredwith third insulating layers 21A, 21B and 210.

The MTJ element A is provided in the third insulating layer 21C. Theupper end of the MTJ element A is connected to the bit line BL via theupper electrode 17. The lower end of the MTJ element A is connected to asource/drain diffusion layer 34B of the select transistor 2 via acontact wiring BEC embedded in the third insulating layers 21A and 21B.A source/drain diffusion layer 34A of the select transistor 2 isconnected to the bit line bBL via a contact wiring bBEC in the thirdinsulating layer 21A.

The select transistor 2 is configured as a field effect transistorhaving a planar structure. That is, the select transistor 2 includes agate electrode 33 on an active region AA between the source/draindiffusion layer 34A and the source/drain diffusion layer 34B with a gateinsulating film 32 interposed therebetween. The gate electrode 33extends in the row direction and is used as the word line WL.

In addition to the above, the MTJ element A provided in the thirdinsulating layer 21C may be the MTJ element B and the MTJ element C.

Regardless of the example of FIGS. 9A to 9E, the MTJ element A may bearranged at a position shifted from just above the contact wiring BEC.Specifically, the MTJ element A may be arranged above the gate electrode33 or the like of the select transistor 2, for example, using anintermediate wiring layer.

Furthermore, the select transistor 2 may be a field effect transistorhaving a three-dimensional structure. Examples of the field effecttransistor having a three-dimensional structure include Recess ChannelArray Transistor (RCAT), and FinFET. The RCAT has a structure in which agate electrode is embedded in a recess in a semiconductor region via agate insulating film. The FinFET has a structure in which the gateelectrode 33 three-dimensionally intersects rectangular semiconductorregions via a gate insulating film.

Regardless of the example of FIG. 11, two memory cells MC may beprovided adjacent to each other in the column direction within oneactive region. In this case, the two memory cells MC are provided so asto share one bit line bBL and source/drain diffusion layer 34A. Thereby,the cell size of the memory cell MC is reduced.

For example, when the magnetoresistive effect element according to thepresent embodiment is mounted on the memory cell array, themagnetoresistive effect element in the memory cell array includes thosein which the first magnetic layer 14 and the conductive layer 19 are notin contact with each other. Since the first magnetic layer 14 and theconductive layer 19 may be in contact with each other in a formationprocess, to cause a short-circuit path, the second insulating layer 20is provided as the insurance. Therefore, in the magnetoresistive effectelement according to the present embodiment, a magnetoresistive effectelement in which the first magnetic layer 14 and the conductive layer 19are not in contact with each other is also included in the scope of thepresent invention.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A magnetoresistive effect element comprising: afirst magnetic layer; a nonmagnetic layer provided on the first magneticlayer; a second magnetic layer provided on the nonmagnetic layer; afirst insulating layer provided at least on a side surface of the secondmagnetic layer; a second insulating layer covering at least a part ofthe first insulating layer; a conductive layer provided between thefirst insulating layer and the second insulating layer; and a firstelectrode including a first portion on the second magnetic layer and asecond portion on a side surface of the second insulating layer, whereina height of a lower surface of the second portion is equal to or lessthan a height of an upper surface of the conductive layer.
 2. Themagnetoresistive effect element of claim 1, wherein a height of an uppersurface of the first insulating layer is greater than a height of anupper surface of the second magnetic layer.
 3. The magnetoresistiveeffect element of claim 1, wherein the second insulating layer covers aside surface of the first magnetic layer and the conductive layer. 4.The magnetoresistive effect element of claim 1, wherein the conductivelayer is in contact with the first magnetic layer.
 5. Themagnetoresistive effect element of claim 1, wherein the first insulatinglayer covers the nonmagnetic layer.
 6. The magnetoresistive effectelement of claim 1, wherein the second insulating layer further covers atop surface of the first insulating layer.
 7. The magnetoresistiveeffect element of claim 1, wherein the conductive layer contains atleast one element of a plurality of elements contained in the firstmagnetic layer.
 8. The magnetoresistive effect element of claim 1,further comprising a third insulating layer provided around the secondinsulating layer.
 9. A magnetic memory comprising: a plurality of memorycells, wherein at least one of the plurality of memory cells includesthe magnetoresistive effect element of claim
 1. 10. A magnetoresistiveeffect element comprising: a first magnetic layer; a second magneticlayer; a nonmagnetic layer provided between the first magnetic layer andthe second magnetic layer; a first insulating layer including a portionfacing at least the second magnetic layer in a second directionintersecting a first direction from the first magnetic layer toward thesecond magnetic layer; a second insulating layer including a portionfacing the first insulating layer in the second direction; a conductivelayer provided between the first insulating layer and the secondinsulating layer; and an electrode including a first portion facing thesecond magnetic layer in the first direction and a second portion facingthe second insulating layer in the second direction, wherein, in thesecond direction, at least a part of the second insulating layer isprovided between the second portion and the conductive layer.
 11. Themagnetoresistive effect element of claim 10, wherein the firstinsulating layer includes a portion facing the first portion in thesecond direction.
 12. The magnetoresistive effect element of claim 10,wherein the second insulating layer covers the conductive layer and thefirst magnetic layer in the second direction.
 13. The magnetoresistiveeffect element of claim 10, wherein the conductive layer is in contactwith the first magnetic layer.
 14. The magnetoresistive effect elementof claim 10, wherein the first insulating layer covers the nonmagneticlayer.
 15. The magnetoresistive effect element of claim 10, wherein thesecond insulating layer covers the first insulating layer to face thefirst portion of the electrode.
 16. The magnetoresistive effect elementof claim 10, wherein the conductive layer contains at least one elementof a plurality of elements contained in the first magnetic layer. 17.The magnetoresistive effect element of claim 10, further comprising athird insulating layer provided around the second insulating layer. 18.A magnetic memory comprising: a plurality of memory cells, wherein atleast one of the plurality of memory cells includes the magnetoresistiveeffect element of claim
 10. 19. A magnetoresistive effect elementcomprising: a first magnetic layer; an electrode including a firstportion and a second portion surrounding the first portion in a seconddirection along a plane intersecting a first direction from the firstmagnetic layer toward the first portion; a nonmagnetic layer providedbetween the first magnetic layer and the first portion; a secondmagnetic layer provided between the first portion and the nonmagneticlayer; a first insulating layer surrounding the second insulating layerin the second direction; a second insulating layer surrounding the firstinsulating layer in the second direction; and a first conductive layerprovided between the first insulating layer and the second insulatinglayer, wherein at least a part of the second insulating layer isprovided between the second portion and the first conductive layer inthe second direction.
 20. The magnetoresistive effect element of claim19, wherein the conductive layer is in contact with the first magneticlayer.
 21. The magnetoresistive effect element of claim 19, wherein thefirst insulating layer covers the nonmagnetic layer.